Less than prime
What is the sum of all integer values of \(n\) satisfying \(1 \leq n \leq 100\), such that \(n^2 - 1\) is a product of exactly two distinct prime numbers?
Details and assumptions
The number \(12= 2 \times 2 \times 3\) is the product of 3 (not necessarily distinct) prime numbers. With reference to this question, 12 is not the product of exactly two distinct prime numbers.